• Journal of Bio-Environment Control
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• v.8 no.3
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• pp.152-163
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• 1999

It is required to analyze the controlled response of air temperature in greenhouse according to control techniques for precise control. In this study, a mathematical model was established for air heating of greenhouse with hot-water heating system The parameters of the model were decided by regression analysis using reference data measured at the greenhouse being heated In the simulation for the digital control of air temperature in the greenhouse, the mathematical model to evaluate the control performances was used. Tested control methods were ON-OFF contpol, p control, rl control and PID control. The mathematical model represented by inside air temperature ( T$_{i}$), hot-water temperature (T$_{w}$) in heating pipe and outside air temperature (T$_{o}$) was expressed as a following discrete time equation ; T$_{i}$($textsc{k}$＋1)＝ 0.851.T$_{i}$($textsc{k}$)＋0.055.T$_{w}$($textsc{k}$)＋0.094.T$_{o}$($textsc{k}$) Control simulations for various control methods showed the settling time, the overshoot and the steady state nor as follows; infinite time, 3.5$0^{\circ}C$, 3.5$0^{\circ}C$ for ON-OFF control : 30min 2.37$^{\circ}C$, 0.51$^{\circ}C$ for P control; 21min, 0.0$0^{\circ}C$, 0.23$^{\circ}C$ for PI control; 18min 0.0$0^{\circ}C$, 0.23$^{\circ}C$ for PID control, respectively. PI and PID controls appeared to be optimal control methods. There was no effect of differential gain on the heating process but much effect of integral gain on it.on it.

• Nuclear Engineering and Technology
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• v.41 no.6
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• pp.849-858
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• 2009

Risk caused by safety-critical instrumentation and control (I&C) systems considerably affects overall plant risk. As digitalization of safety-critical systems in nuclear power plants progresses, a risk model of a digitalized safety system is required and must be included in a plant safety model in order to assess this risk effect on the plant. Unique features of a digital system cause some challenges in risk modeling. This article aims at providing an overview of the issues related to the development of a static fault-tree-based risk model. We categorize the complicated issues of digital system probabilistic risk assessment (PRA) into four groups based on their characteristics: hardware module issues, software issues, system issues, and safety function issues. Quantification of the effect of these issues dominates the quality of a developed risk model. Recent research activities for addressing various issues, such as the modeling framework of a software-based system, the software failure probability and the fault coverage of a self monitoring mechanism, are discussed. Although these issues are interrelated and affect each other, the categorized and systematic approach suggested here will provide a proper insight for analyzing risk from a digital system.

• Journal of Broadcast Engineering
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• v.2 no.1
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• pp.8-15
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• 1997

In this paper, a real-time operating Motion Picture Experts Group-1 (MPEG-1) audio encoder system is implemented using a TMS320C31 Digital Signal Processor (DSP) chip. The basic operation of the MPEG-1 audio encoder algorithm based on audio layer-2 and psychoacoustic model-1 is first verified by C-language. It is then realized using the Texas Instruments (Tl) assembly in order to reduce the overall execution time. Finally, the actual BSP circuit board for the encoder system is designed and implemented. In the system, the side-modules such as the analog-to-digital converter (ADC) control, the input/output (I/O) control, the bit-stream transmission from the DSP board to the PC and so on, are utilized with a field programmable gate array (FPGA) using very high speed hardware description language (VHDL) codes. The complete encoder system is able to process the stereo audio signal in real-time at the sampling frequency 48 kHz, and produces the encoded bit-stream with the bit-rate 192 kbps. The real-time operation capability of the encoder system and the good quality of the decoded sound are also confirmed using various types of actual stereo audio signals.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.810-812
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• 1998

Analog I&C hardwares in most of nuclear power plants in operation are aging since they were installed 1950's or 1960's. Thus, the replacement of such systems with digital computer-based systems is currently a new trend in nuclear area. This paper will discuss such transition occurring in nuclear I&C area, Comparative study on the digital technique adopted in leading nuclear industries. Its advantage and performance evaluation will be illustrated as well.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.645-650
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• 2000

this paper deals with HVDC Light(High Voltage Direct Current) system using space vector PWM(SVPWM) method. Because the system of this paper has d-q control scheme for HVDC Light system. HVDC Light system represented in this paper is capable of controlling active and reactive power independently. For this system. V-I curve and control methods are proposed. Also this paper describes the design of a digital system for applications in power converters such as those that would be used in the next generation of HVDC system. Finally HVDC system is implemented using DSP TMS320C31

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.10a
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• pp.219-224
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• 2003

Recently, the number of the use of Digital Photogrammetry is increasing, the Digital Photogrammetry is used for the acquisition of images, remote sensing and three dimension location. Especially, the three dimension location is more activated to use digital camera for the Digital Photogrammetry. The reason is that it is cheap and easy to use and also it has high confidence. Using non-metric digital camera not metric camera, in this research, to get images and apply the images to the Direct Liner Transformation which is one of the techniques in Digital Photogrammetry to get three dimensional location of a point. Ⅰ programmed the procedure with Visual C++ to get the position of points speedly and I tested possibility whether it can analyze the displacement and the existence of structure with measurement system which is structured by a inexpensive non-metric digital camera.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.32 no.12
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• pp.441-449
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• 1983

Recently, various kinds of computers with architecture different from the usual type of Neumann and Data flow machine have been studied for inproving computational speed. Among them, Feed Forward Computer(F.F.C.) has been remarkably developed. F.F.C. is a computer different from usual digital one in operating system. The usual computer executes operation and operand Fetch after executing instruction fetch and instruction decode. But conceptually, F.F.C. excutes instruction fetch, instruction decode operand fetch and combinational execution simultaneously. Accordingly, a suitable software is needed to operate high reliability and efficiency of this F.F.C. system. In this study, I aim at developing characteristics on highly reliable computer system which should be a blueprint of F.F.C. system in the future.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.379-381
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• 1999

This paper presents a study of the performance of a brushless DC motor (BLDCM) speed control system. Recently, most motor controls are implemented in digital electronics. Digital controllers tend to be more accurate, less susceptible to noise and more flexible in terms of programming. The system used a digital PI controller in order to implement the constant speed of Brushless DC motor. Microprocessor used in this experiment is 80c196kc. The applied motor has been constructed using a 50W, 150V, 3000rpm, four-pole motor.

• The KIPS Transactions:PartC
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• v.8C no.6
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• pp.757-764
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• 2001

The increase of electronic commerce leads to the increasing attention to the way customers pay and a large number of researches on payment system. Recently many researches on a system which provides anonymity in order to protect user\`s privacy have been carried out. And some potential problems from that system are being reviewed by anonymity control system. This thesis will include the following. First, I want to analyze the old scheme related to divisible and examine general ideas of anonymity control. Second, I propose a new blind signature in addition to KCDSA, the standard digital signature in Korea. The last one I want to propose is a new electronic cash system with the divisible for more efficient use of electronic cash which can control anonymity with the help of trustee.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.3
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• pp.70-79
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• 1993

The application of A.C. motor to servo system is rapidly increased according to the recent advance of power electronics and digital control techniques. The induction motor which has a simple structure and needs less maintenance is used in the industrial field for the variable speed and position control recently. In this paper, the current characteristic of the full-bridge resonant inverter is studied by comparing with the computer simulation and the laboratory experiment when the ratio of forced frequency to the natural frequency and the ratio of conduction time to the period at the given frequency is changed. And then, the full-bridge resonant inverter is applied to the speed control of single phase induction motor.